Straw-bale Construction

The purpose of sustainable architecture is to minimize negative ecological effects on structures, while simultaneously providing for the optimal health and happiness of those within them. 

Straw bale construction is an exciting new building technique that fits perfectly within the ideals of sustainability and is suitable for a huge range of African projects.

What is Straw-Bale Construction?

Straw bale building uses straw bales for both internal insulation and load-bearing walls of structures. They are packed into blocks and then reinforced with bamboo or wood to create the wall components. Then cover the walls with natural clay stucco to keep the bales dry and safe from weathering.

Straw is an agricultural waste product, making its use in construction part of sustainable, renewable resources. Straw bale walls also offer great insulation which means energy saving on the heating and air-conditioning side. Straw-bale house building materials are also affordable and readily available in Africa.

Environmental and Economic Benefits

Environmental and economic factors have made straw bale construction of residential as well as commercial buildings more prevalent over recent years.

Low Environmental Impact

Compared to conventional wood and concrete buildings, bale buildings have a stunningly low ecological footprint. The straw itself is agro-waste which is usually burnt as garbage! That’s a whole lot of straw that won’t be in landfills, and less toxic emissions entering our atmosphere.

Straw is another regrowing raw material that locks in carbon as it grows in the field. On the whole, they consume very little carbon and combat in their way against GES (Green House Effect).

Affordability

Straw, wood poles or posts, and plaster (much cheaper than concrete, steel, and timber). Straw being a byproduct from wheat, rice etc. has next to zero extra cost as raw material for construction.

Building with straw bales is not as skilled and time-consuming as most conventional building techniques. This keeps labor costs affordably low and makes building oneself accessible for more homeowners. The total cost of building can be as low as 50% of that of the typical stick-built residence.

Thermal Insulation

Straw is nature’s perfect insulator — keeping straw-bale homes toasty in the winter and comfortable in the summer months. Thick straw bale walls provide better insulation than standard wood frame walls. This can cut the energy cost of heating and cooling over the service life of the building.

Durability

Well-built and finished with stucco, straw-bale houses are extremely robust and can continue to exist for centuries with minimal maintenance. Thick walls provide safety to the building against moisture, rodents, fire, and more.

Construction Process

Laying foundations — Building a straw bale house requires several important steps from foundation to detail. Here is an overview of the general process:

Foundation

Heavy timber framing was used as it could easily carry the weight of the balcony floor above and the heavy bale walls that were to be constructed on top. Footing and floor slabs or stone footings are the best options here. Drainage must be taken into account to help avoid any moisture problems.

Frame and Bale Placement

After the base layer has been finished, wood poles/timber posts are raised in order to construct the frame of load-bearing walls. Regular size dimensions are typically 24 in x 18-20 in). The straw bales are then layered between the columns like laying bricks using stems to bond them on alternate sides.

Roof installation

The timber beams and trusses are installed for roof framing. It is typically made of corrugated metal (or other water-shedding materials) to shed water away from the bale walls.

Electrical and Plumbing

Plaster in before there is any electrical wiring or running plumbing. Bale cores are best protected with reinforcement inside pipes where they cross the bale core.

Plastering

Now both sides of the bales are being covered in an earth plaster protective coating. This adheres to and watertight seals the reed from weather and animals while reinforcing its load-carrying capacity.  Multiple layers may be required to achieve a satisfactory depth of renders on walls.

Finishing Touches

Finish out the inside with drywall, floor, utility rough-ins, and other finishes. The exterior will be paint-stain/exposed brick. Landscaping finishes off the build.

Straw-Bale Construction Techniques

There are a few techniques for constructing straw-bale buildings:

• Load-bearing walls–The stacks hold up the roof and structural components.

• Infill walls — A separate wooden or bamboo framework holds up the roof, with straw bales serving as the insulation.

• Hybrid — Bearing 1st floor and infill 2nd floor (to reduce loading).

• Bale-stacking designs — stacked with the running bond, stacked as if they were adobe blocks laid in place.

• Truth window headers — fake “windows” built in bale walls for decoration.

Becoming skilled at these crafts enables us to create gorgeous, eco-friendly straw bale builds.

Integrating Modern Comforts

While straw-bale construction utilizes natural materials, modern comforts can still be integrated:

• Electric conduit and plumbing routed through pre-cut grommets in bales.

• Solar panels for reusable energy; and rainwater harvest systems to store water.

• Sunlight was captured and brought in as much as possible using intelligent design of windows.

• Passive solar design: thermal mass floors.

• Active solar systems incorporating hydronic heating in floor.

Combining of natural raw materials along with intelligent technology gives rise to the green building trends.

Conclusion

When correctly designed and built, the practice of straw-bale construction presents a very sustainable approach to housing and commercial structures in Africa. 

 Its abundance of locally sourced raw materials, natural self-regulating indoor climate, longevity and low cost make it a highly suitable approach for addressing the ongoing shortage of adequate housing in addition to the consequences of climate change. 

Straw bale techniques continue to evolve further, bringing the ecological and economic advantages of this sustainable construction method closer to more neighborhoods.